Why Can't I Stop?

Every time we have that board meeting, my heart races. It's not the stress of work, it's Sarah. Every time she speaks up with those brilliant ideas, I feel like a giddy kid at Disneyland. Lately, it's been hard to focus on anything else during meetings because I'm too busy thinking about how her hair looks when she leans over paperwork or how her laugh lights up the room. It feels weird and wrong to have these thoughts about my coworker while we're in such professional settings. Is this normal? Am I just being overly dramatic, or is there something unhealthy happening here? How do I deal with it without making things awkward?